A home-schooled teenager named Bree is heating up the Internet like few others today.

But is she for real? Or is she merely an actress? If so, who are the people responsible for mounting the charade?

This Internet whodunit centers on 16-year-old Bree's "Lonelygirl15" online video diaries, posted on sites such as YouTube and MySpace. They've caused a cyber-stir not seen since "The Blair Witch Project."

The mystery has fueled the popularity of the short videos that are a staple on a growing number of Web sites devoted to posting homemade entertainment.

On sites such as Revver and Guba, regular people are posting videos that range from confessional diaries to stunts involving everything from skateboards to breath mints dropped into bottles of Diet Coke.

Many feature people just sitting in front of video cameras, talking about the mundane happenings in their lives or ranting about some issue or another.

On YouTube, one of the most popular sites for amateur videos, 26,930 people are subscribed to the Lonelygirl15 "channel," meaning they regularly view videos posted there.

More than 2.3 million people have viewed Bree's videos, according to YouTube.

Lonelygirl15 started posting her dorky adventures in June, with a video that looked like so many others on the Web.

"Bree" is sitting in her typical-looking teenage room, introducing herself and making a variety of goofy faces.

In subsequent "episodes" (so far, she has posted more than 30 videos with the latest entry posted Sept. 10), Bree talks about her parents, her friend Daniel and her "religion," which includes a mysterious ritual Bree has been selected for.

The ceremony only takes place "once in a really long while" and attendance is limited to a select few.

"My parents won't even be allowed to come," Bree says.

The ceremony also involves memorization and "special exercises" that Bree's mother is going to help her with. Plus, she has to go on a diet.

"Other than that, it's basically like preparing for a bar mitzvah or a confirmation," Bree says matter of factly.

The mystery deepens. In her room is what looks like a shrine to the occult figure Aleister Crowley, leading many Bree-watchers to assume she is involved in some kind of Satanic cult.

Then, several weeks ago, rumors began to fly that Bree was not a genuine teen blogger at all, but an actress playing a part in scripted and produced drama.

The proof, it was said, is that Bree never reacts on-screen to comments posted about her, never wavers from the plot.

So far, even as media attention heats up about her authenticity, Bree has yet to react in her videos.

Fans began to speculate that the videos were part of a big marketing campaign for some movie and bristled at being manipulated by some Hollywood studio.

The most notable Web hoax related to movie publicity was for the 1999 film "The Blair Witch Project."

Footage from an alleged documentary about a mysterious video tape and missing teens created a buzz on the Web that helped boost the film's box-office success.

The marketing theory surrounding Lonelygirl15 was bolstered when amateur sleuths uncovered that the name was trademarked recently by Encino attorney Kenneth Goodfried, who did not return a call seeking comment Monday.

Web detectives also concluded that Bree's MySpace account was being controlled by someone using a computer at the Hollywood talent firm Creative Artists Agency. An agency spokesman did not immediately return a call Monday.

And then came the announcement posted on the mock fan site Lonelygirl15.com stating that Bree was indeed an actress.

"Thank you so much for enjoying our show so far," said the note, signed only "The Creators" and addressed to "our incredible fans."

The note, posted Sept. 7, continued: "Right now, the biggest mystery of Lonelygirl15 is `who is she?' We think this is an oversimplification. Lonelygirl15 is a reflection of everyone. She is no more real or fictitious than the portions of our personalities that we choose to show (or hide) when we interact with the people around us."

The "Creators," who describe themselves as filmmakers but not part of a big corporation, go on to promise a new Web site featuring interactive storytelling where "the line between 'fan' and 'star' has been removed, and dedicated fans like yourselves are paid for their efforts."

But in the strange world of Lonelygirl15, nothing can be trusted. Soon after the message was posted, the Web site could not be accessed.

It was running again over the weekend, where two new episodes were posted, but was only intermittently available on Monday.

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